1. Field of the Invention
The present invention relates to a positioning device for an inspection device for inspecting a magnetic reading and writing head, a magnetic disc or the like, and more particularly to a rotary style positioning device.
2. Description of the Related Art
A hard disc device (HDD), which is an external memory device of a computer, has made a remarkable development in recent years. It is a recording and reproducing head that has contributed to such a remarkable development. A dynamic test (an R/W test=a Read after Write Test) used for the quality control is extremely important, and a precise drive device referred to as a spin stand is normally used in this R/W test. Since a structure close as much as possible to that of a HDD is desirable for the spin stand, the rotary style for positioning the head by the swing of the head is ideal.
However, there is a problem in that since the type that allows all the positioning with one actuator out of the conventional rotary positioning stages is controlled at a constant positioning resolution over all the strokes, the moving speed is slow even in the case where the stroke is long when the resolution is set to a high level. That is, even in the case where so precise positioning is not required (a rough motion), there is also a problem in that the motion speed is slow in the same manner as the case in which the stroke is short and a precise positioning is conducted.
On the other hand, the type having a double structure stage in which the stage is separated into a rough motion stage and a slight motion stage is intended to solve a function conforming to an object by providing a double structure of the precise motion and the rough motion and by using different actuators for respective movements in order to improve a disadvantage in that a motion speed is slow. However, the type having a double structure of stages, a rough motion stage and a slight motion stage becomes complicated in structure and the mechanical rigidity of the whole stage is lowered so that there arises a problem in that a settling time becomes long and a high speed and highly precise positioning cannot be conducted.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotary positioning stage that enables a high speed and a highly precise positioning.
In order to solve the above problems, after deliberate consideration, the inventors of the present invention take note of the fact that only extremely short stroke (e.g., 5 xcexcm or less) is demanded in the test of the hard disc head, so that when the motion quantity is extremely small, the geometric error (an error of 0.5 xcexcm or less with respect to the motion quantity of 5 xcexcm) between a straight line motion and a rotational motion becomes so small that the error can be ignored, and have come to an idea that the actuator for the rotation of the rotary stage is moved in a direction of a straight line. Furthermore, when a speed reducing mechanism is used, a load inertia of the moving mass applied to the actuator via the speed reducing mechanism is theoretically square of the speed reducing ratio. Thus, the inventors of the present invention have come to the idea that a mechanical speed reducing mechanism is provided on the rotary positioning stage by taking note of the fact that the moving mass can be largely decreased.
A first aspect of the present invention is completed on the basis of the idea described above and provides a rotary positioning stage which comprises: a rotary stage rotatably supported on a rotation shaft and provided with an arc-like portion for forming an arc with respect to the rotation shaft, the stage allowing attachment of a work (e.g., workpiece); first positioning means provided with a pulley contacting the arc-like portion for positioning the work by rotating the rotary stage via the pulley; and second positioning means for positioning the work by slightly moving the first positioning means in a straight line-like manner in a tangent line direction at a contact point between the arc-like portion and the pulley.
A second aspect of the present invention provides a rotary positioning stage characterized in that the arc is formed in such a manner that the length from the rotation shaft to the art-like portion is formed in a range of 25 mm to 100 mm and the center angle is formed to 40 degrees or more, and the radius of the pulley is formed in a range of 5 mm to 20 mm while the second positioning means moves the first positioning means in a straight line-like manner within the range of 5 xcexcm or less in addition to the structure according to the first aspect of the invention.
When the slight motion quantity of the first positioning means is in the range of 5 xcexcm or less, the geometric error between the straight line motion and the rotational motion becomes so small that the error can be ignored. As a consequence, when the rotary stage is rotated in the range of 5 xcexcm or less, the work can be positioned at a high precision by the second positioning means.
A third aspect of the present invention provides a rotary positioning stage characterized in that the stage is formed at a ratio between the length from the rotation shaft to the arc-like portion and the radius of the pulley ranging from a range of 1:1 to 10:1.
Here, the speed reducing ratio is set within the range of 1:1 to 10:1. Preferably, the ratio is set to 3:1 to 7:1, and most preferably, the ratio is set to 5:1.
A fourth aspect of the present invention provides a rotary positioning stage wherein the first positioning means is provided with a belt which is wound in an approximately crossing manner with respect to the arc-like portion and the pulley for rotating the rotary stage with the rotation of the pulley in such a manner that the rear surface runs along the external circumferential surface of the pulley and the surface runs along the external circumferential surface of the arc-like portion.
The first positioning means transmits the drive force generated from the drive source of a motor or the like to the arc-like portion of the rotary stage via a belt wound around the pulley and the arc-like portion. Since the belt is wound around the pulley and the arc-like portion in an approximately crossing manner, the pulley winds up the belt wound around the arc-like portion so that the rotary stage is rotated. That is, when the pulley is rotated, a part of the belt wound around the arc-like portion in advance is released to be wound by the pulley. Furthermore, a part of the belt wound around the pulley in advance is released to be wound by the arc-like portion. In this manner, the rotary stage is rotated by mutually winding up the belt between the pulley and the arc-like portion.